You also have to remember that the ducks do not need to be there permanently. Evaporation is around 30 inches in this part of the world. If you put 25-50 ducks in for a year and keep track of rainfall and the water level of the pond. If the leak is fixed you don't have to keep them. Stock your freezer with duck, stock a bunch of fish and feed their entrails to the fish.
There really is no such thing as an "invasive" plant. Its just a plant that finds a niche that is not already taken up in your newly created ecosystem and thrives. If you fill that niche before that plant arrives it cannot grow, there's no space for it.
But you really cannot battle mother nature, she has a set number of rules you must play by, or your stuck in a cycle of burning/slashing/ and poisoning to control plants you don't understand
